Rape is a serious physical assault that has devastating long-term physical and emotional effects. The extensiveness and seriousness of this problem demands a concerted, effective social response. Substantial evidence indicates that sexual aggression is determined by a multiplicity of variables and is committed by a heterogeneous group of offenders. The present research proposal is designed to address three critical issues about the assessment of sexual aggression. First, the investigators propose to continue validation research on an easily administered and processed inventory, the Multidimensional Assessment of Sex and Aggression (MASA), for which both computerized and paper-and-pencil administration forms exist. This inventory has been designed to assess the critical domains that discriminate among sex offenders, and it has already demonstrated some evidence of reliability and validity. The investigators propose to improve the MASA by expanding its assessment of both the developmental antecedents of aggression and of domains critical to the evaluation of child molesters. Second, the investigators propose to use the MASA to revise and simplify our rapist typology (the Massachusetts Treatment Center Typology for Rapists [MTC-R3], which is currently the only empirically validated, reliable typology for rapists. Third, the investigators propose to continue the development of a version of the MASA for juvenile sex offenders and to use this instrument to develop a valid typology for this population.